The present invention is concerned with piston rings for internal combustion engines, particularly with oil control rings. More specifically, the present invention is concerned with a one-piece oil control ring adapted to be received within a peripheral groove formed in the piston of an internal combustion engine. The oil control ring of the invention, like oil control rings in general, provides one or more scraper rims whose function is to scrapingly engage the cylinder wall to control the distribution of oil thereon.
Such oil control rings in general comprise split annular, generally circular rings. The prior art shows some rings of generally U-shaped cross section having scraper rims on the outer peripheral face thereof and sidewalls projecting inwardly of the ring and within or against which are received the projecting legs of an expander spring which serves to provide the outward bias necessary for proper functioning of the ring. The U-shaped ring and the expander spring are separate components of a two-component assembly.
Such two-component assembly is shown, for example, in U.S. Pat. No. 3,606,359, assigned to the assignee of this application, and is illustrated in FIG. 4 thereof.
The prior art also shows three component oil scraper ring assemblies. One such is shown in FIG. 5 of the aforesaid U.S. Pat. No. 3,606,359. In this type of prior art arrangement a pair of split annular, circular flat rail rings are engaged with a generally U-shaped expander ring which engages the rail rings and urges them outwardly of the groove in scraping engagement with the cylinder.
It is also known to utilize an expander spring which itself provides an edge serving as a scraper rim against the wall of the cylinder, as well as serving to engage a rail ring in scraping engagement with the cylinder wall. Such an arrangement is shown in U.S. Pat. No. 3,628,800 also assigned to the assignee of this application.
Numerous other prior art arrangements of two and three piece oil control assembly rings are shown, for example, in U.S. Pat. Nos. 2,635,022, 2,744,803 (assigned to the assignee of this application), 3,140,096 and 3,384,383.
Generally, two-component oil control ring assemblies are utilized in medium duty gasoline and diesel truck engines. In high temperature, severe environment of such engines, three-component assemblies are subject to being stuck together by lacquer-like residues formed from combustion of the fuel and lubricants, which lacquer tends to misalign the components resulting in poor performance.
Three-component oil control ring assemblies are normally used in passenger car gasoline engines, in which the less severe conditions ameliorate the sticking problem.
At the other extreme of engine power, light duty gasoline engines such as those used on snow blowers, gasoline powered lawn mowers, etc. are also subject to the sticking problem resulting in misalignment of the components.
A number of problems are encountered by such multi-component assembly rings. One problem is production difficulties encountered in assembling the several components of the ring assembly into properly aligned and interengaging relationship with each other within the groove of a piston. The advantage of a single piece or unitary assembly in this respect is obvious. The unitary oil control ring assembly of the invention is believed to be most advantageously employed in light duty gasoline engines such as used in powered lawn mowers, snow blowers etc., but its use is not limited thereto.
A second problem with multi-component ring assemblies is that in operation of the engine proper alignment and engagement of the components with each other may be lost. For example, under the stress of operation in which high inertial forces are imposed on the ring assembly and with wear of the parts, there is a tendency for rail rings to tilt out of position or to otherwise shift so that the most effective oil scraping action is lost.
Finally, it will be appreciated that a manufacturing sequence which admits of producing what may be termed an oil control ring "assembly" in a unitary piece, has manufacturing advantages over the production, stocking and assembly of separate parts.
It is accordingly an object of the present invention to provide a unitary, i.e., one-piece, oil scraper ring which provides one or more scraper rims and biasing means and may therefore be termed a unitary oil control ring assembly.
It is another object of the present invention to provide an oil scraper ring which is economically manufactured and which has characteristics of rigidity and dimensional accuracy which provides excellent oil scraping performance.
Unitary compression piston rings, but not oil control rings, having integral spring fingers cut therefrom are known. For example, U.S. Pat. No. 1,288,085 issued Dec. 17, 1918, shows a piston ring R from which tongues 2 "possessing a certain degree of inherent resiliency" are struck. These tongues are adapted to contact the bottom wall of the groove to urge the ring R outwardly.
Similarly, U.S. Pat. No. 2,311,557 issued Feb. 16, 1943 to William S. Mason utilizes integral readially resilient means for urging the ring periphery against the wall of the cylinder. In this case spring fingers 11 projecting inwardly of the compression ring to urge it into contact with the cylinder wall.
In accordance with the present invention, there is provided an oil control piston ring of generally annular construction which has a peripheral wall, from the outer face of which projects at least one and preferably two scraping rims and from which are cut a plurality of spring members which project inwardly of the ring from the inner face of the peripheral wall thereof a distance sufficient to engage the bottom wall of the groove within which the ring is disposed in order to bias the ring outwardly sufficiently to engage the scraping rim or rims with the cylinder wall. That is, the spring members or at least a portion thereof define the radially innermost portion of the ring. When two scraping rims are employed they are axially spaced from each other and preferably have flat scraping faces.
In accordance with one aspect of the present invention there is provided a one-piece, annular oil control ring assembly of generally U-shaped cross section defined by a peripheral wall from which two sidewalls extend radially inwardly of the ring, and which has at least one and preferably two scraping rims which project radially outwardly of the peripheral wall, a plurality of spring members cut from the peripheral wall and extending from the inner face thereof more radially inwardly of the ring than the innermost peripheries of the sidewalls whereby the spring members can engage the bottom wall of the groove sufficiently so that a radially inwardly acting compression force imposed on the ring will bend the spring members sufficiently to bias the scraping rims radially outwardly.
In accordance with another aspect of the invention, the one-piece oil control ring assembly, i.e., the one-piece oil control ring, is provided with a plurality of debris openings in the peripheral wall thereof. In accordance with a preferred aspect, the debris openings are provided by the cut outs which form the integral spring members.
The oil control ring of the invention is adapted to be received within a peripheral groove in a piston received within a piston cylinder so that the ring spring members bias the ring to urge the scraping rims thereof into contact with the cylinder wall.